That's been my takeaway.
Extremely low internal impedance so if you need very large burst current they're the best choice, this is why you use big honking caps in large electric motors to buffer that big instantaneous draw. Still though with modern lithium batteries having some rather stout burst current potential AND just so much more energy reserve I don't think they're terribly practical for the cost unless you're getting a super good deal on them.
Have you seen any evidence of this being anything measurable or audible? I find it hard to believe that anything outside of the junk drawer by way of amplifiers don't have adequate capacitance built into the power supply for them to function as intended within their rated operating range.
I'll reach out to someone who knows more about that realm and see if I can get some input, but I'd like to think that <1500W or so there's no reason your wall outlet is going to drop voltage or anything, and there's no reason that throwing the same money into batteries (lithium or AGM) shouldn't get you damn close to the same end result as supercaps in a vehicle.
That all said, there is one guy up here in the northeast that has a proper dB Drag SPL vehicle that just uses a large cap bank but it ONLY needs to do 3 second burst. Now would he get the same numbers spending dollar for dollar on some modern lithium? Who can say, I don't think he'll ever need to replace them for a few shows a year they're going to outlast the vehicle by far.